Pneumatic drives have been used to operate landing gear for trailers. These systems have been installed as original equipment and as conversion kits to convert conventional manually operated mechanisms that raise and lower the landing gear, such as hand crank mechanisms, to automatic pneumatically driven systems.
Typically, such pneumatic systems include air motor drives. The air motor drives a transmission that in turn drives the existing conventional landing gear shaft. Pressurized air can be taken from the existing brake line to drive the motor. Brake lines generally extend from the tractor to the rear wheels of the trailer. A valve is positioned between the brake line and the motor to control the rotational direction of the motor as well as to turn the motor on and off.
Generally, these pneumatic systems have been designed to be mounted to the undercarriage of the trailer body. While these designs permit the pneumatic system to be mounted to a flatbed type trailer, they are not suitable for mounting to trailers not having a flatbed, such as trailers having a cylindrical body (e.g., tankers).
Specifically, if the pneumatic motor were to be bolted to the tanker, the bolts would extend into the tanker. Among the drawbacks associated with this mounting arrangement is leakage. Obviously, leakage creates a serious hazard when the substance being transported is extremely volatile or toxic. Although welding is an alternative to mechanical fasteners, there are numerous factors that must be considered before welding the pneumatic system to the cylindrical body of a tanker.
Tankers typically are made of aluminum, a metal that generally is difficult to weld. The pneumatic motor would have to have an aluminum portion to provide metallurgical compatibility with the aluminum tanker. Further, aluminum welds preferably are made using the tungsten inert gas (TIG) process. The TIG process is not only slow and thus costly, it requires a relatively high degree of skill, thereby limiting the feasibility of field installation.
Even if the tanker was made of stainless steel, other disadvantages associated with welding remain. For example, the explosive nature of residue in the tanker must always be considered. After the tanker has been used to transport volatile substances, welding the pneumatic system directly to the tanker would be undesirable for obvious reasons. Again field installation generally would may not be feasible.
Therefore, there is a need to provide a pneumatic system having a universal mounting arrangement that can be coupled to trailers of different configuration for automatically raising and lowering the landing gear of a trailer.
It has been found that the transmission between the output shaft of the pneumatic motor and the crank shaft in known pneumatic systems also present certain disadvantages. The existing crank shaft provided with conventional landing gear is designed to axially translate within the high-low gear reducer that also is conventionally provided with the landing gear. This translation provides interchangeability between high and low gear in the crank shaft gear reducer. The abovementioned transmissions include gears directly connected to the output shaft of the pneumatic motor and the landing gear crank shaft. If the crank shaft could be translated, the gears no longer would mesh. Accordingly, this arrangement renders the crank's high-low gear reducer system inoperable.
Therefore, there is a further need to provide a pneumatic lift that does not interfere with the intended operation of the gear reducer that is provided as standard equipment with conventional landing gear.